An existing base station (BS) communicates with user equipment (UE) in a broadcasting manner in which a beam is extremely wide, coverage is wide, user equipment in a same sector of beams can be distinguished only by frequencies, each user equipment occupies small bandwidth in a given frequency bandwidth, and a system capacity is small because time-division multiplexing is used. By contrast, a millimeter wave has a higher frequency band and a narrower beam. A high-gain directional narrow beam may be implemented by using a beamforming technology, so that each user equipment can perform space division multiplexing/frequency division multiplexing by using multiple narrow beams to obtain a multiplexing gain and improve a communication capacity.
In beamforming technology, an antenna distance needs to be not greater than ½ of a wavelength. However, in a line of sight (LOS) situation, non-correlation of multiple-input multiple-output (MIMO) channels requires an antenna distance to be greater than a specific value, and a greater antenna distance indicates a lower antenna correlation. Therefore, for a large-scale array antenna system with a high frequency band, because an antenna diameter is limited and an antenna distance is relatively small, it is difficult to meet a Rayleigh length of LOS-MIMO so as to ensure non-correlation between MIMO channels. In a conventional technology, communication quality of a MIMO communications system is relatively poor.